It is known that a surfactant composition containing a polyglycerol monoalkyl ether and a polyglycerol dialkyl ether is suitably used in the applications such as cosmetics and detergents because the composition can exhibit a good emulsification effect for forming an emulsion having an excellent stability with time.
For example, Patent Document 1 discloses a polyglycerol alkyl ether-type nonionic surfactant having a polyglycerol monoalkyl ether content of 75% by weight or more and a polyglycerol dialkyl ether content of 5% by weight or less.
Patent Document 2 discloses a cosmetic composition or detergent composition containing a polyglycerol 2-ethylhexyl ether in which an average number of 2-ethylhexyl groups added to a polyglycerol is 1.5 or more.
Also, Patent Document 3 discloses a two-part hair dye composition having a gentle effect on skin which is free from sagging of foams for a period from application to hair up to rinsing because the hair dye composition can maintain a good foaming property even at a low temperature. The two-part hair dye composition disclosed in Patent Document is constituted of an alkaline agent and a hydrogen peroxide agent at least one of which contains a polyglycerol alkyl ether having a specific composition including 75% by weight or more of a polyglycerol monoalkyl ether (monoalkyl compounds), 5% by weight or less of a polyglycerol dialkyl ether (dialkyl compounds) and 20% by weight or less of a polyglycerol.